Abstract. Is the fraction of anthropogenically released CO₂ that remains in the atmosphere increasing? Is the rate at which the ocean and land sinks take up CO₂ from the atmosphere decreasing? We analyze these questions by means of a statistical dynamic multivariate model from which we estimate the unobserved trend processes together with the parameters that govern them. By assuming a balanced global carbon budget, we obtain more than one data series to measure the same object (for example, the airborne fraction). Incorporating these additional data into the dynamic multivariate model in effect increases the number of available observations, thus improving the reliability of parameter estimates. We find no statistical evidence of an increasing airborne fraction but we do find statistical evidence of a decreasing sink rate. We infer that the efficiency of the sinks to absorb CO₂ from the atmosphere is decreasing at approximately 0.54% per year.